Ladder filter and duplexer

a duplexer and ladder filter technology, applied in the field of ladder filters, can solve the problems of difficult to further promote miniaturization, and achieve the effects of enhancing the disposition density of resonators, reducing the dimensions in the propagation direction of elastic waves, and reducing the dimensions of elastic wave propagation
US20130002372A1Active Publication Date: 2013-01-03MURATA MFG CO LTD
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
MURATA MFG CO LTD
Publication Date
2013-01-03

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Abstract

A ladder filter including a series arm resonator and a parallel arm resonator disposed on the same common piezoelectric substrate achieves improved miniaturization. The ladder filter includes series arm resonators and parallel arm resonators, which include elastic wave resonators, and are disposed on the same common piezoelectric substrate, at least one parallel arm resonator of the series arm resonators and the parallel arm resonators includes a first resonator and a second resonator electrically connected in parallel to each other, and the first resonator and the second resonator are arranged in parallel or substantially in parallel in a direction perpendicular or substantially perpendicular to an elastic wave propagation direction, on one side outside one series arm resonator of remaining resonators in the elastic wave propagation direction thereof.
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Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a ladder filter including a plurality of elastic wave resonators. In more detail, the present invention relates to a ladder filter including a series arm resonator and a parallel arm resonator, which include elastic wave resonators, located on one piezoelectric substrate, and a duplexer including the ladder filter, defining at least one band pass filter.

[0003] 2. Description of the Related Art

[0004] In the past, ladder filters have been widely used as band pass filters for mobile phones. In addition, in this type of ladder filter, so as to achieve miniaturization, a series arm resonator and a parallel arm resonator are configured using surface acoustic wave resonators.

[0005] For example, in Japanese Unexamined Patent Application Publication No. 2000-201052, an example of such a ladder filter is disclosed. FIG. 8 is a plan view schematically illustrating this ladder filter.

[0006] In the ladde...

Claims

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